Relative Resistance of Potato Tubers Produced from Stem Cuttings and Seed-Piece-Propagated Plants to Streptomyces scabies. Rosemary Loria, Associate Professor, Department of Plant Pathology, Cornell University, Long Island Horticultural Research Laboratory, Riverhead, NY 11901. Barbara A. Kempter, Research Technician, Department of Plant Pathology, Cornell University, Long Island Horticultural Research Laboratory, Riverhead, NY 11901. Plant Dis. 70:1146-1148. Accepted for publication 7 May 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1146.

Tubers can be produced from axillary buds on stem cuttings taken from potato plants. Infection of such tubers by Streptomyces scabies was compared with infection of tubers produced from seed-piece-propagated plants, using lesion surface area (%) and lesion type as criteria. Under greenhouse conditions, the scab lesions on tubers produced from stem cuttings and seed-piece-propagated plants appeared similar. Nine of 11 isolates of S. scabies tested were pathogenic on tubers produced from both stem cuttings and seed-piece-propagated plants of the scab-susceptible potato cultivar Chippewa. Lesion surface area ratings on tubers from stem cuttings grown in the greenhouse and seed-piece-propagated plants grown in naturally infested soil in the field were highest for Chippewa, intermediate for Katahdin, and lowest for Superior. Similar varietal differences in lesion type ratings were expressed in tubers grown from seed-piece-propagated plants in the field. Lesion type ratings on tubers produced from cuttings were lowest for Superior but were similar for Chippewa and Katahdin. The potential for using tubers produced from cuttings to screen potato clones for resistance to common scab and for ecological research on S. scabies is discussed.